Oleaginous drilling fluid that produces a useful soil amendment, method of use and bio-remediation of the same and resulting solids

ABSTRACT

A biodegradable wellbore fluid with an oleaginous phase including a linear paraffin having 11-18 carbon atoms, a non-oleaginous phase, an emulsifying agent and optionally a weighting agent. Use of the fluid while drilling allows bio-remediation of drill cuttings using land spreading, bioreactors, conventional composting or vermiculture composting. The resulting product, especially when vermicomposed, is potentially useful as a soil amendment or plant fertilizer material.

[0001] This application claims the priority benefit of U.S. ProvisionalApplication No. 60/268,635, filed Feb. 14, 2001, and U.S. ProvisionalApplication No. 60/269,204, filed Feb. 15, 2001, and U.S. ProvisionalApplication No. 60/269,752, filed Feb. 19, 2001, and U.S. ProvisionalApplication No. 60/298,765, filed Jun. 16, 2001.

BACKGROUND OF THE INVENTION

[0002] Drill cuttings are the earth, rock and other solid materialsgenerated during the rotary drilling of subterranean wells. The drillcuttings are removed from beneath the drill bit by a stream of drillingfluid that suspends the solids and carries the solids to the surface. Onthe surface, the drill cuttings are separated from the drilling fluid ina drilling cuttings separator or shaker and the drill cuttings arecollected at the drill site for subsequent treatment.

[0003] Traditional oleaginous drilling fluids, also known as oil-baseddrilling fluids or invert emulsion drilling fluids (if they contain aninternal non-oleaginous phase), may be harmful to marine life due to thepresence of aromatic hydrocarbons in the diesel fuel or other similarpetroleum fractions used as the continuous phase. The development oflow-toxicity mineral oil-based drilling fluids—with very low fractionsof aromatic compounds—allayed much, but not all, of the concern overacute toxicity effects on marine flora and fauna. However, discharge ofmud-laden cuttings still produces a mound of cuttings on the ocean floorthat may smother any marine life that resides on the seabed.

[0004] Development of synthetic-based drilling fluids as alternatives toconventional oil-based drilling fluids in offshore operations wasprecipitated by residual toxicity and biodegradability concerns. Thesedevelopments focused on the fate and effects of oil-coated drilledcuttings discharged into the sea, as well as worker safety. For onshoreapplications, cuttings disposal is also of importance. However, sincethe drilled cuttings are disposed of on land, the environmental issuesfocus primarily on subsequent usability of the land and contamination ofground water. Although the advent of synthetic-based fluids has greatlyimproved the environmental acceptability of non-aqueous drilling fluidsboth offshore and onshore, current synthetic-based fluid formulationsstill present problems for direct land treatment of oil-coated cuttingsresulting from onshore operations. The concerns with pollution of soiland groundwater by synthetic based fluids and oil-based fluids have ledto increasingly strict government regulations.

[0005] Oily drill cuttings can have severe impacts on their receivingenvironment and should be cleaned or treated to minimize theirenvironmental impact and the operator's long term liability. The primarypurpose of each of these methods is to somehow destroy or remove thedrilling fluid residue from the earth solids. In addition to the abovementioned method of land treatment (spreading and farming), there is alitany of other ways to treat oil-coated cuttings from drillingoperations. These include landfill disposal; bio-remediation;stabilization/solidification (briquetting, fixation with silicates orfly ash); extraction or washing (oil, detergents, and solvents); andthermal treatment (incineration and distillation, including thermaldesorption and hammer mill). The treatment of drill cuttings is thesubject of a number of patent applications and literature disclosuresthat include U.S. Pat. Nos. 6,187,581; 6,020,185; 5,720,130; 6,153,017;5,120,160; 5,545,801; 4,696,353; 4,725,362; 4,942,929; 5,132,025. Thesepatents describe various methods of treating oily drill cuttingsincluding incineration; reinjection of the slurrified cuttings intoanother subterranean formation; chemical washing and landfill disposal;and other methods. As noted above, the primary purpose of each of thesemethods is to somehow destroy or remove the drilling fluid's residuefrom the earth solids.

[0006] Despite considerable research conducted in the area of drillcuttings disposal, there remains an unmet need for a clean, inexpensiveand environmentally friendly drilling fluid and method of treating thedrill cuttings such that they produce an end product that may have abeneficial use.

SUMMARY OF THE INVENTION

[0007] The present invention is generally directed to a drilling fluid,a method of drilling, and a method of treating drilling fluid waste. Inparticular, the present invention provides a biodegradable, low-toxicitydrilling fluid which enables bio-remediation of drill cuttings into abeneficial product using land spreading or farming with optionalpre-treatment in bioreactors or through composting.

[0008] An oleaginous drilling fluid has been developed that possessesthe drilling properties of conventional oil-based and synthetic-baseddrilling fluids but which can be discharged (as fluid-coated drilledcuttings) onto land to provide minimal detrimental effects on animal andplant life. The individual components of this environmentally friendlyfluid—base fluid, internal non-oleaginous phase (if the oleaginousdrilling fluid is an invert emulsion), emulsion stabilizers, wettingagents, fluid-loss reducing agents and weighting agent—also possessthese attractive features.

[0009] The drilling fluid may be used without any treatment of thedrilled cuttings in areas where restrictions on farming or spreading ofthe cuttings on land have prohibited use of a typical synthetic-basedfluid or oil-based fluid. For areas where restrictions are even moresevere, e.g. where essentially zero discharge is required, the drillingfluid may be used in conjunction with rapid bio-remediation or otherpre-treatment to produce cuttings with less than 1% residual base fluid.

[0010] The present invention also encompasses methods of bioremediationof the drilling cuttings generated during drilling operations using thefluids disclosed herein. IN one such preferred illustrative embodiment,drilling cuttings are mixed with sawdust and transported to abioremediation site. At the bioremediation site, the mixture of drillingcuttings and sawdust is mixed with paunch waste and then applied towindrows designed for vermi-composting.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a graphical representation of exemplary sample datashowing the effect of temperature on biodegradation rate of linearparaffin based drilling fluid on simulated cuttings in a bioreactor.

[0012]FIG. 2 is a graphical representation of exemplary sample datashowing the effect of time on oxygen uptake rate (OUR) and % oil and/orsynthetic drilling fluid on cuttings (ROC) of an linear paraffin baseddrilling fluid on simulated cuttings in a bioreactor at 25° C.

[0013]FIG. 3 is graphical representation of exemplary sample datashowing chromatographic analysis of hydrocarbon content of cuttings in acomposting trial over a period of 42 days in which the seven groupscorrespond to the seven linear paraffins used in the base fluid.

[0014]FIG. 4 is graphical representation of the exemplary sample datashowing total petroleum hydrocarbon content detected by GC-FID (mg/kgdry weight)from the first test of vermicomposting.

[0015]FIG. 5 is graphical representation of exemplary sample datashowing the total petroleum hydrocarbon content detected by GC-FID(mg/kg dry weight) from the control sample of the second test ofvermicomposting.

[0016]FIG. 6 is graphical representation of exemplary sample datashowing the total petroleum hydrocarbon content detected by GC-FID(mg/kg dry weight) from the 30% w/w application rate sample of thesecond test of vermicomposting.

[0017]FIG. 7 is graphical representation of exemplary sample datashowing the total petroleum hydrocarbon content detected by GC-FID(mg/kg dry weight) from the 50% w/w application rate sample of thesecond test of vermicomposting.

[0018]FIG. 8 is graphical representation of exemplary sample datashowing the total petroleum hydrocarbon content detected by GC-FID(mg/kg dry weight) from the 70% w/w application rate sample of thesecond test of vermicomposting.

[0019]FIG. 9 is graphical representation of exemplary sample datashowing the total petroleum hydrocarbon content detected by GC-FID(mg/kg dry weight) from the 100% w/w application rate sample of thesecond test of vermicomposting.

[0020]FIG. 10 is graphical representation of exemplary sample data ofthe average total petroleum hydrocarbon content detected by GC-FID(mg/kg dry weight) for all application rates of the second test ofvermicomposting.

[0021]FIG. 11 is graphical representation of exemplary data of the soilpH values at the initial starting point (T=0) and endpoint (T=60 days).

[0022]FIG. 12 is graphical representation of exemplary data of the soilelectrical conductivity values at the initial starting point (T=0) andendpoint (T=60 days).

[0023]FIG. 13 is graphical representation of exemplary data of the soilsoluble salt content values at the initial starting point (T=0) andendpoint (T=60 days).

[0024]FIG. 14 is graphical representation of exemplary data of the soilammonium nitrogen concentration values at the initial starting point(T=0) and endpoint (T=60 days).

[0025]FIG. 15 is graphical representation of exemplary data of the soilnitrate nitrogen concentration values at the initial starting point(T=0) and endpoint (T=60 days).

[0026]FIG. 16 is graphical representation of exemplary data of the soilnitrite nitrogen concentration values at the initial starting point(T=0) and endpoint (T=60 days).

[0027]FIG. 17 is graphical representation of exemplary data of the soilphosphate phosphorous concentration values at the initial starting point(T=0) and endpoint (T=60 days).

[0028]FIG. 18 is graphical representation of exemplary data of the soilbarium concentration values at the initial starting point (T=0) andendpoint (T=60 days).

[0029]FIG. 19 is graphical representation of exemplary data of the soilheavy metal concentration values at the initial starting point (T=0) andendpoint (T=60 days).

[0030]FIG. 20 is graphical representation of exemplary data of thehydrocarbon concentration values determined by GC-FID (mg/kg dry weight)over time of the third test of vermicomposting.

DETAILED DESCRIPTION OF THE INVENTION

[0031] A new synthetic-based fluid has been developed that minimizesenvironmental impact and actually provides needed soil nutrients byreplacing one or more of these four major components withenvironmentally friendly materials. This fluid maintains the excellentdrilling engineering properties of conventional synthetic-based fluidsand oil-based fluids.

[0032] The following terms and phrases are used herein and are intendedto have the following meaning:

[0033] “ES” is Electrical Stability (API RP 13B-2), V;

[0034] “GC-FID” is Gas Chromatograph with Flame Ionization Detector,

[0035] “HTHP” is High Temperature, High Pressure;

[0036] “IC₅₀” is Concentration of Test Material at which the rate ofbioluminescence of bacteria used in a Microteox test is reduced by 50%;

[0037] “LP” is Linear Paraffin;

[0038] “OUR” is Oxygen Uptake Rate, mg/L/min;

[0039] “OWR” is ratio of [% Oleaginous Fluid]/[% Water], calculated sothat the sum of the two phases=100%;

[0040] “ROC” is Retained Fluid on dried Cuttings, % w/w, and

[0041] “SOC” is Synthetic Fluid on Dried Cuttings, % w/w.

[0042] The present invention is directed to a biodegradable,low-toxicity drilling fluid to facilitate (1) drilling a wellbore and(2) bio-remediation of the drill cuttings.

[0043] Oleaginous drilling fluids generally contain some components,such as excess lime and clays, which are intrinsically beneficial tomany soils. Low pH (<5.5) is detrimental to most agricultural crops, andoften soil needs to be treated with an alkaline material like lime tocounter-act the effects of low pH. Clays can act as soil conditioners,especially for sandy soil, by improving its texture and increasing itswater-holding capacity. In addition, some organics, especially thosesimilar to humus, serve as nutrients and conditioners.

[0044] The major components of conventional prior art oleaginousdrilling fluids, on the other hand, may not be so beneficial. Suchcomponents may include (a) oleaginous base fluid; (b) non-oleaginousfluid; (c) emulsifier/surfactant package; and (d) weighting agent. Anyone of these may affect seed germination, plant growth and/or the lifecycle of native fauna, e.g. earthworms. The present invention overcomesthese limitations by formulating an invert emulsion drilling fluid thatis suitable for bio-remediation.

[0045] The amount of oleaginous base fluid in the drilling fluid of thepresent invention may vary depending upon the particular oleaginousfluid used, the particular non-oleaginous fluid used, and the particularapplication in which the drilling fluid is to be employed. However,generally the amount of oleaginous base fluid must be sufficient to forma stable emulsion when utilized as the continuous phase. Typically, theamount of oleaginous base fluid is at least about 30, preferably atleast about 40, more preferably at least about 50 percent by volume ofthe total fluid. The oleaginous base fluid may be any oleaginous basefluid suitable for use in formulating an invert emulsion drilling fluidbase fluid, however it is important the oleaginous fluid be compatiblewith the bio-remediation and biodegradation goals of the presentinvention. With this proviso in mind, the oleaginous base fluid mayinclude substances such as diesel oil, mineral oil, synthetic oil,saturated and unsaturated paraffins, branched paraffins, ester oils,glycerides of fatty acids, aliphatic esters, aliphatic ethers, aliphaticacetals, or other such hydrocarbons and combinations of these fluidssuitable for use in a drilling fluid. However, such a fluid shouldpreferably be substantially composed of paraffin. That is to say thepredominant component is preferably paraffin. Especially preferred arelinear paraffins, and more preferably linear paraffin having 11 to 18carbon atoms. One preferred illustrative embodiment of the presentinvention utilizes a commercially available C₁₁-C₁₈ linear paraffinmaterial sold under the tradename BIO-BASE 560, available from M-I LLC.of Houston, Tex. Another preferred illustrative embodiment utilizes acommercially available C₁₂-C₁₃ linear paraffin sold by Sasol.

[0046] The amount of non-oleaginous fluid in the drilling fluid of thepresent invention may vary depending upon the particular fluid used, theparticular oleaginous fluid used, and the particular application inwhich the drilling fluid is to be employed. However, generally theamount of non-oleaginous fluid must be sufficient to form a stableemulsion when utilized as the internal phase, also known as thediscontinuous phase, of the drilling fluid. The internal non-oleaginousfluid generally is an aqueous solution containing one or more of thefollowing: a non-electrically conductive material, e.g. an alcoholincluding glycerin, glycols, polyols; a salt containing a biodegradableanion, preferably formate ion more preferably in the form of sodiumformate, or acetate such as calcium magnesium acetate (CMA); a saltcontaining a soil-nutrient-anion and possibly cation, preferably nitrateion in the form of calcium nitrate, ammonium calcium nitrate, orphosphate ion preferably potassium pyrophosphate. In one preferred andillustrative embodiment of the present invention, the non-oleaginousfluid is substantially free of halide ion. That is to say, the amount ofhalide ion is such that the halide content is suitable forbio-remediation and biodegrading of the drilling fluid or any resultingcuttings. In one illustrative embodiment, the fluid is formulated suchthat halide-containing salts typically used in drilling fluidformulation, (e.g. potassium chloride, potassium bromide, and otherhalide salts) are not used in the formulation of the non-oleaginousphase. This results in a non-oleaginous phase that does notsubstantially increase the halide salt content of the soil into whichthe biodegraded drilling fluid or cuttings are applied. Typically theamount of non-oleaginous fluid is less than about 90, preferably lessthan about 70, more preferably less than about 50 percent by volume ofthe total fluid.

[0047] One illustrative version of the non-oleaginous fluid internalphase is a nitrate brine. Another illustrative version uses acetatebrine as the internal phase. A third illustrative version of theinternal phase is a blend of the nitrate and acetate brines. A blend ofacetate and nitrate salts of one illustrative embodiment was found to beparticularly suited for direct land treatment of muddy cuttings,inasmuch as the acetate is intrinsically biodegradable while the nitrateaccelerates the overall biodegradation process.

[0048] As with the other components of the inventive drilling fluidformulation, the emulsifier package utilized to stabilize the invertemulsion and maintain oil-wetting character of the drilling fluid shouldbe biocompatible and not adversely affect the biorememdiation process.That is to say the emulsifier package used to stabilize the emulsiondrilling fluid should be a biodegradable material. Further, theemulsifier should be present in an amount sufficient to stabilize theinvert emulsion so that the invert emulsion can be used as a drillingfluid. Especially preferred in one illustrative embodiment is eurisicdiglyceride, but other emulsifiers suitable for forming oleaginousdrilling fluids may also be used. Thus, in one illustrative embodiment,blends of commercial emulsifiers, such as NOVAMUL and VERSAWET bothavailable from M-I Houston, Tex. with eurisic diglyceride are used toform stable invert emulsion suitable for use as an invert emulsiondrilling fluid.

[0049] In addition to the oleaginous fluid, non-oleaginous fluid andemulsifier package used in the drilling fluids of the present invention,other components typical of oleaginous drilling fluids, and well knownin the art, may be used. For example, in one illustrative embodiment,viscosifying agents, for example, organophilic clays, are employed inthe invert drilling fluid compositions utilized as part of the presentinvention. Other viscosifying agents, such as oil soluble polymers,polyamide resins, polycarboxylic acids and fatty acid soaps may also beemployed. The amount of viscosifying agent used in the composition willnecessarily vary depending upon the end use of the composition. Usuallysuch viscosifying agents are employed in an amount which is at leastabout 0.1, preferably at least about 2, more preferably at least about 3percent by weight to volume of the total fluid. In one exemplarydrilling fluid an organophilic clay is used, preferably an organophilicclay that is a high yield clay and tolerant to high temperatures.Especially preferred in this illustrative embodiment is BENTONE 38available from M-I Houston, Tex.

[0050] Another typical additive to oleaginous drilling fluids that mayoptionally be included in the oleaginous drilling fluids of the presentinvention are fluid loss control agents such as modified lignite,polymers, oxidized asphalt and gilsonite. Usually such fluid losscontrol agents are employed in an amount which is at least about 0.1,preferably at least about 1, more preferably at least about 3 percent byweight to volume of the total fluid. The fluid-loss reducing agentshould be tolerant to elevated temperatures, and inert or biodegradable.Especially preferred is ECOTROL available from M-I, Houston, Tex.

[0051] The illustrative invert oleaginous fluids used and disclosed asbeing within the present invention may optionally contain a weightingagent. The quantity and nature of the weight material depends upon thedesired density and viscosity of the final composition. In one suchillustrative embodiment, the weight materials utilized include, but arenot limited to, hematite, barite, ilmenite, calcite, mullite, gallena,manganese oxides, iron oxides, mixtures of these and the like. Theweight material is typically added in order to obtain a drilling fluiddensity of less than about 24, preferably less than about 21, and mostpreferably less than about 19.5 pounds per gallon. The weighting agentshould be inert or innocuous to the conditions of bioremediationespecially if the product is to be dissolved by low-pH soil. In one suchillustrative embodiment, hematite (FER-OX) or calcium carbonate(SAFE-CARB) are selected as preferred weighting agent. Hematite mayprovide iron to iron-poor soils. Barite as a weighting agent is lessdesirable than other weighting agents especially if a formate salt isused in the internal phase. In the presence of formate ion some solublebarium are formed (400 ppm was measured at room temperature). Likewise,some dissolution barite may occur in low-pH environments, such as acidsoils, making the use of barite as a weighting agent less desirable thanother potential weighting agents.

[0052] One skilled in the art may readily identify whether theappropriate ingredients and amounts have been used to form a usefuloleaginous drilling fluid by performing the following test:

[0053] Oleaginous Slurry Test: A small portion of the formulated slurryis placed in a beaker that contains an oleaginous fluid. If the slurryis an oleaginous, it will disperse in the oleaginous fluid. Visualinspection will determine if it has so dispersed.

[0054] Alternatively, the electrical stability of the formulated slurrymay be tested using a typical emulsion stability tester. For this test,the voltage applied across two electrodes is ramped upward, and, if theslurry is an invertemulsion, a surge of current will flow at the voltagewhere the emulsion breaks. The voltage required to break the emulsion isa common measure of the stability of such an emulsion. One of skill inthe art should know and understand that as the breakdown voltageincreases, the stability of the invert emulsion increases. Other testsfor determining the formation and stability of an invert emulsiondrilling fluids are described on page 166 of the book, Composition andProperties of Drilling and Completion Fluids, 5th Edition, H. C. H.Darley and George Gray, Gulf Publishing Company, 1988, the contents ofwhich are hereby incorporated by reference.

[0055] One illustrative method of bioremediation of the drilling fluidsand drilling cuttings generated by using the fluids of the presentinvention includes the use of a bioreactor. Bioreactor treatment isdesigned to provide accelerated aerobic or anaerobic biodegradation in acontrolled environment, and generally involves slurrification of thebiodegradable waste in water or other carrier fluid. In one suchillustrative aerobic bioreactor operation, the oleaginous drillingfluid-coated drill cuttings are dispersed in a quantity of water, spikedwith a bacterium designed to metabolize hydrocarbons, and the entireslurry aerated continuously with air. The biodegradation rate isdetermined from measurements of Dissolved Oxygen (DO) and Oxygen UptakeRate (OUR).

[0056] The biodegradation process exhibits an induction period as thebacteria population increases. This is manifested in the rapid increaseof the Oxygen Uptake Rate. In one illustrative example, simulated drillcuttings coated with a lab-prepared oleaginous slurry prescribed by thisinvention were treated in an aerobic bioreator at room temperature (e.g.25° C.) using no additional nutrient and only moderate aeration. Whenthe fuel (fluid on the cuttings) depleted to a synthetic oil fluid oncuttings (ROC) of about 3% w/w (after about 7 days), the rate ofbiodegradation peaked and began to fall rapidly. By 15 days, ROC hadfallen to <1% w/w, and the rate had reached a plateau beyond whichlittle reduction in ROC is observed. By contrast, cuttings coated with aconventional diesel-based mud with CaCl₂ brine internal phase exhibits aROC of about 7% w/w even after 21 days.

[0057] Temperature is an important factor in optimizing the bioreactorprocess. Indeed, increasing the temperature by about 10° C. (to 35° C.)cuts the time required for OUR to drop to near-baseline levels (andROC<1% w/w) as shown in the graphical representation of the exemplarydata given in FIG. 1. Increasing the temperature beyond 35° C. resultsin little gain for most bacteria, and above 40° C.,hydrocarbon-metabolizing bacteria generally begin to lose activity.

[0058] As important as the operating temperature is, efficient transportof oxygen and the presence of other nutrients are equally important toefficient operation of a bioreactor. Modifying the flow of air to ensurehigher and more homogeneous values of Dissolved Oxygen increases thebiodegradation rate. Similarly, comminution of the cuttings and/orintroducing mechanical mixing can enhnace the rate. Various nutrients,especially nitrat, can also olay a role in the degradation process.Spiking the mixture with a general-purpose fertilizer (containingpotassium and phosphate along with nitrate) produces enhancedbiodegradation rates, and maintaining a high fertilizer content produceshigher sustained biodegradation rates.

[0059] Another illustrative method of bio-remediation of the drillingfluid solids and cuttings generated by using the fluids of the presentinvention is conventional composting. During conventional composting,heat generated by microbial decomposition is retained within a pile orcompost vessel, and degradation of the material occurs in a number ofdistinct phases according to the dominant types of bacteria at any giventime. The pile/vessel is initially colonized by mesophilic organismsthat grow best at ambient temperatures, but as the material degrades andheat builds up in the pile/vessel (usually rising to 50° C. within twoto three days), they are superseded by thermophilic organisms thatthrive at high temperatures (50-60° C.). These higher temperatures aremore favorable for rapid biodegradation and are used in some composts tokill potentially harmful pathogens in a process similar topasteurization. As only thermo-tolerant organisms can survive at thehigher temperatures, the microbial numbers start to decline, and thecomposting material cools. At this stage anaerobic conditions maydevelop, unless sufficient air is introduced. In the third stage, thematerial continues to cool and the microorganisms compete for theremaining organic material, leading to a breakdown of cellulose andlignins etc. During the final, maturation stage, levels of microbialactivity continue to decline as the remaining food is used up and themicroorganisms die off.

[0060] Whereas bioreactor treatment is generally a fluid process(slurrification of solid or liquid biodegradable material), conventionalcomposting primarily involves solids. Windrowing (mechanical or manualturning of the material) and forced aeration of static biopiles are thecommonest methods, although there are also methods of mixing andaerating the material based on rotating reactors. The rotary compostingvessel has a small footprint and can be used to continuously process thecuttings waste stream. The mixing imparted by the gradual rotation ofthe drum (0.5 rpm) is enough to ensure adequate aeration of thecomposting mixture. Use of an insulated drum improves heat retention ofthe composting mixture and increases the rate of degradation. Oil-coateddrill cuttings may be mixed together with another solid organicsubstance that is also reasonably readily degraded, e.g. straw or woodchips. This mixture may be supplemented with nitrogen, phosphorous andpossibly other organic nutrients.

[0061] The present invention is also directed to a method ofbio-remediation of drill cuttings using vermiculture, also called wormculture or vermicomposting. In particular, the present illustrativeembodiment provides a high efficiency process for the biodegradation ofdrill cuttings using vermiculture and vermicomposting beds. Vermiculturecan provide worms as a raw material for an animal feed ingredient, liveworms for sport fishing, or for other product uses. Vermicomposting isthe use of worms to break down waste materials such as livestock manureand municipal waste. Generally, worms consume inorganic and organicmatter, digest and absorb largely organic matter, and pass the remainderback to the soil. As a result of their feeding behavior, worms aid inthe breaking down of organic material within the material they consume.The activity of worms also ventilates the soil and promotes bacterialand other microbial decomposition processes.

[0062] Large-scale vermiculture typically uses beds in which largequantities of organic material are worked by worms in a relativelystationary mode. The vermicomposting beds also called windrows aretended to and the materials are provided in a batch process. Turning or“freshening” of the beds by introduction of bedding materials is carriedout using specialized vermiculture farm machines well known to one ofskill in the art. After the organic material is substantially brokendown, the worms and digested material are separated and harvested.

[0063] The term “vermicomposting” as used here is understood to be thebreakdown of organic matter by the ingestion and digestion of the matterby worms. Vermicomposting also includes the collateral biotransformationof such organic matter from the bacterial action inherent in suchsystems. As such the present invention is also an apparatus and processfor worm production by exposing the worms to the compositions of thepresent invention. There is believed to be at least hundreds of speciesof what are commonly known as “red” worms in the vermicompostingtechnology. One example is the Lumbricus rubellus another is Eseniafoetida. Generally, the species of red worm is not important tovermicomposting and while the red worms used to demonstrate the presentinvention were Esenia foetida, other types will work equally, dependingsomewhat upon the type of organic matter and environment. That is to saythat other species of earthworm may be used in addition or instead of“red” worms such as Esenia foetida. As the term is used in the presentdescription, “worm” is intended to include all types and specie ofearthworm that can be utilized in the vermi-composting of organicmaterials.

[0064] Methods of vermicomposting and vermiculture should be well knownto one of ordinary skill in the art. For example, U.S. Pat. Nos.2,867,005; 3,635,816; 4,262,633; 4,187,940; 5,451,523; 6,223,687;6,654,903 all describe differing methods of vermicomposting andvermiculture. The contents of each of these patents are herebyincorporated herein by reference.

[0065] In the practice of the present illustrative embodiment, drillcuttings are blended with a bulking agent to facilitate transport to thetreatment site. Examples of such bulking agent include: sawdust, woodshavings, rice hulls, canola husks, shredded newsprint/paper; shreddedcoconut hulls, cotton seed hulls, mixtures of these and other similarmaterials. The cuttings and bulking agent are preferably blended with acompostable waste material prior to further treatment at the treatmentsite. Examples of suitable compostable waste include yard or householdwastes, food preparation or processing wastes, paunch or rumen materialor similar animal rendering wastes, sewage sludge from a water treatmentfacility and mixtures of these and other similar materials. The mixingprocess is carried out so as to give the optimumcarbon:nitrogen:moisture balance prior to spreading. Because thebio-remediation of the mixture is an aerobic process, the optimumconditions for worm driven waste management of these materials is 75%(w/w) moisture, with a carbon nitrogen ratio of 25:1.

[0066] The mixture of drill cuttings and nitrogenous materials is thenvermicomposted. Preferably this is carried out by spreading the mixtureonto windrows or specialized/mechanical worm beds where the worms ingestthe material further degrading the cuttings and excreting the resultingworm cast which is collected and subsequently used as a fertilizer orsoil conditioner.

[0067] An optional intermediate stage carried out prior to spreading isto pre-compost the cuttings mixture. Such pre-vermiculturepre-composting is carried out in a traditional manner of compostingorganic materials. Such pre-composting treatment may be desired for anumber of reasons including: a) increase the rate of remediation by theaction of thermolytic micro-organisms and enzymes which make the organicmaterial more available to the degrading organisms; b) reduce the numberof pathogenic micro-organisms present in any of the other components ofthe mixture; c) to reduce the risk of overheating (within the worm beds)through microbial action and thus reduce the activity of the worms.

[0068] The methods of the present illustrative embodiment may be equallyapplied to the treatment of either water-based or oil-based drillingfluids. Such fluids may typically contain olefin, esters, acetals,glycol, starch, cellulose, fish and vegetable oils and mixtures of theseand other organic materials that require treatment prior to disposal. Itis important to note that the selection of such materials shouldpreferably be limited to materials that are not excessively saline ortoxic to the worms. Treatment of such oilfield wastes containinghydrocarbons or any other suitable organic components using the methodsof the present invention may be enhanced by a pre- or co-compostingstage as previously described.

[0069] It may also be possible to effect the scavenging of heavy metalsfrom soils and oilfield wastes based upon the worm's ability tobioaccumulate heavy metals. Preferably this operation would be carriedout prior to disposal and would work in a similar manner tophytoremediation.

[0070] Use of alternative organisms and species, e.g. nematodes or otherworm types is also contemplated and is considered with the scope of thepresent invention. Such alternative organisms include geneticallymodified worms with either enzymes for degradation of problem pollutantsor worms containing genetically modified bacteria able to degradeproblem pollutants at higher rates. Marine vermiculture utilizingorganisms able to work at much higher salt concentration and degrademarine pollutants is also contemplated as being within the scope of thepresent invention.

[0071] The following examples are included to demonstrate illustrativeembodiments of the invention. It should be appreciated by those of skillin the art that the compositions, formulations, and techniques disclosedin the examples which follow represent techniques discovered by theinventors to function well in the practice of and thus are illustrativeof the present invention. As such the following examples can beconsidered to be illustrative of the present invention and constitutepreferred illustrative modes for its practice. However, those of skillin the art should, in light of the present disclosure, appreciate thatmany changes can be made in the illustrative embodiments which aredisclosed and still obtain a like or similar result without departingfrom the scope of the invention.

[0072] All values associated with the formulations described below aregrams unless otherwise specified.

EXAMPLE 1

[0073] The following illustrative embodiment of the present inventiondemonstrates a method of preparing the oleaginous drilling fluid, asuitable test procedure for operation and monitoring of a lab-scalebioreactor, and biodegradability test results of oleaginous base fluids.

[0074] Drilling Fluid Mixing & Testing Procedure

[0075] Test fluids were mixed with a Hamilton Beach (HB) mixer over aperiod of 1 hr, and then exposed to high shear with a Silverson mixerset at 7000 rpm until the slurry reached 150° F. Property measurementsconsisted of initial API Electrical Stability (ES) and API standardrheology at 150° F. After heat-aging (rolling) the fluids for 16 hr at250° F., ES, rheology (again at 150° F.) and API standard HTHP fluidloss at 250° F. were measured. The fluid density was approximately 13.0lb/gal, OWR=70/30, and the water activity of the internal waterphase=0.86 to 0.76 (equivalent to 18 to 24% CaCl₂).

[0076] More rigorous testing included prolonged stability at 300° F. andresistance to the following contaminants: drilled solids (35 lb/bbl OCMAClay), seawater (10% v/v) and weighting agent (increase of density from13 to 15 lb/gal). For these tests the base fluid was mixed in smallamounts over a period of 1 hr on the Silverson at 7000 rpm, maintainingthe temperature at or below 150° F. To three of the portions of basefluid, one of the contaminants was added and mixed in with the HB mixerfor 10 min. As before, initial ES and rheology measurements werefollowed by heat-aging at 250° F. for 16 hr, then ES and rheology (at150° F.) and HTHP fluid loss at 250° F. on half of a lab bbl. The otherhalf of a lab bbl of each sample was heat-aged at 300° F. for anadditional 16 hr, and again ES, rheology (at 150° F.) and HTHP fluidloss (at 300° F.) were determined.

[0077] Bioreactor Test Procedure

[0078] The bioreactor treatment is designed to provide acceleratedaerobic biodegradation in a controlled environment, and generallyinvolves slurrification of the biodegradable waste. Simulated soil ismixed with the drilling fluid to produce muddy “cuttings”, dispersed ina quantity of water, spiked with a bacterium designed to metabolizehydrocarbons, and the entire slurry aerated continuously with air. Thebiodegradation rate is determined from measurements of Dissolved Oxygen(DO) and Oxygen Uptake Rate (OUR). The experimental procedure is asfollows:

[0079] Formulate 4.5 kg of simulated cuttings consisting of ⅓ Texasbentonite, ⅓ Rev Dust and ⅓ Blast Sand #5 (70-140 mesh).

[0080] Spike the cuttings with 1125 mL (1755 g) of mud.

[0081] Add 10 L of aged tap water into the bioreactor, an inverted 5-galwater bottle with the bottom cut out.

[0082] Add 10 g of bacteria/L (˜150 g).

[0083] Slurry 900 g spiked soil with 10 L de-chlorinated tap waterinitially, add 900 g on day 2 and 1800 g on day 4 for a totalconcentration of about 3600 g/15 L or about 240 g/L (18% solids w/w or34% w/v).

[0084] Provide vigorous aeration with aeration device that can provideup to 60 L/min of air.

[0085] Conduct standard API retort analysis of cuttings to determine oilcontent on solids at beginning and end of test.

[0086] Conduct solvent extraction to determine oil content at thebeginning and end of the test for comparison with retort analysis.

[0087] Determine OUR approximately once a day from measurements ofDissolved Oxygen, using a Dissolve Oxygen meter.

[0088] Once a week check pH and maintain in 6-9 range.

[0089] Periodically check nitrogen, along with other potentialnutrients.

[0090] Continue running the retort until OUR drops to a negligiblelevel.

[0091] All values associated with the formulations described below aregrams unless otherwise specified.

[0092] Environmental tests were carried out on the base fluids, severalmuds, and a few samples of mud-coated cuttings before and aftertreatment in a bioreactor. The tests consisted of the following: (a)biodegradability (respiration rate and hydrocarbon loss in a referencemoist soil); (b) phytoxicity (alfalfa seed emergence and rootelongation); (c) earthworm survival; (d) springtail survival; and (e)Microtox (IC-50 on bioluminescent bacterium Photobacterium phosporeum).

[0093] Base Fluid Biodegradability Tests:

[0094] Tables 1 and 2 indicate the relative biodegradability andtoxicity of various Base Fluids. TABLE 1 Biodegradability of VariousBase Fluids % Reduction of Treatment Hydrocarbons Biodegradability RankC₁₁₋₁₄ LP 97 1 C₁₂₋₁₇ LP 94 2 Ester 91 3 Isomerized tetradecene 83 4 C₁₄(IO) Diesel 61 5 Branched Paraffin 43 6

[0095] TABLE 2 Toxicity of Various Base Fluids* Animal Water ToxicityAlfalfa Phytotoxicity Toxicity % Earth- % Root Microtox worm % SeedElonga- Toxicity Treatment IC₅₀ Survival Emergence tion Rank Branched106 100 95 107 1 Paraffin C₁₁₋₁₄ LP 98.5 100 96 134 2 C₁₂₋₁₇ LP 65.9 10095 120 3 Isomerized 61.7 100 101 144 4 tetradecene C₁₄ (IO) Diesel 10.30 7 2 5 Ester 5.9 0 0 0 6

[0096] One of skill in the art will appreciate that the results of Table1 indicate that diesel and the branched paraffins are more resistant torapid biodegradation than the other four fluids. The toxicity data inTable 2 shows that the diesel, and unexpectedly the ester, areconsiderably more toxic than the branched paraffin, linear paraffins(LP's) or isomerized tetradecene internal olefin (IO) in all five tests.The Microtox test also showed some differentiation between the C₁₂₋₁₇ LPand IO (higher toxicity) and C₁₁₋₁₄ LP and branched paraffin (lowertoxicity). This may occur inasmuch as higher molecular weight branchedfluids tend to exhibit lower acute toxicity in tests that focus onwater-column toxicity.

[0097] The toxicity of the ester may be explained by its biodegradationbehavior. GC-FID analysis of soil extracts from all six fluids showsthat only the ester produces non-volatile intermediate degradationproducts, including toxic materials like hexanol, 2-ethyl hexanol,2-ethyl hexanoic acid and 2-ethylhexyl 2-ethylhexanoate. Theseintermediate products constituted about 30% of the ester lost throughbiodegradation.

EXAMPLE 2

[0098] The following illustrative embodiment of the present inventiondemonstrates that the oleaginous drilling fluids of the presentinvention are useful as drilling fluids.

[0099] Standard fluid properties of three 13 lb/gal, 70/30 SWR(Synthetic/Water Ratio) formulations, one with an acetate brine(Formulation A), one with a nitrate brine (Formulation N) and the othera nitrate/acetate blended brine (Formulation NA) are shown in Table 3. Aconventional high-performance diesel-based mud with CaCl₂ brine internalphase gives standard properties that are very similar. The threeformulations in Table 3 were also hot-rolled for 16 hr at 300° F., aswell as 250° F. with essentially no degradation in rheology orelectrical stability (ES).

[0100] Biodegradability and toxicity of Formulations A and N arecontrasted with those of typical diesel/CaCl₂/barite fluid in Table 4.The leading rate on the test soil in Table 4 was 6% w/w. These resultsshow that fluids A and N both are consistently more biodegradable andmuch less toxic than the diesel mud. In comparing formulation A with asimilar formulation weighted with barite (instead of hematite),biodegradability and toxicity appear to be similar for the two fluids.However, a soil-enhancing iron source is considered desirable for itslong-term potential benefits.

[0101] Except for the Springtail survival data, Formulation A showedconsistently lower toxicity than Formulation N. This trend appears tocorrelate with the trend in electrical conductivity (EC) measured afterthe biodegradation test, i.e. after 65 days. Thus, a fluid with a higherEC may generally give a higher toxicity, i.e. toxicity increases withincreasing ionic strength. That Formulation A gives such a low EC isthought to be the result of relatively rapid biodegradation of theacetate ion.

[0102] The toxicity data for the fluid formulation in Table 4 indicatethat the % Root Elongation observed for Formulation A is nearly 50%greater than or the control. This suggests that Formulation A may serveto enhance some aspects of the quality of the soil. TABLE 3 StandardProperties of two Paraffin-Based Fluids Formulation FormulationFormulation Component (g) A NA N BIO-BASE 560 144 143.7 143.5 BENTONE 385.0 5.0 5.0 Lime 3.0 3.0 3.0 ECOTROL 5.0 5.0 5.0 NOVAMUL 8.0 8.0 8.0VERSAWET 2.0 2.0 2.0 CMA Brine 97.0 — — 50/50 Brine Blend at 1.27 SG —115.1 — (28% by wt CMA and 50% by wt ENVIROFLOC) ENVIROFLOC Brine (40% —— 112.9 by wt at 1.20 SG) FER-OX 283 267.1 263.9 Rheology at Hot HotHot- 150° F. Initial Rolled* Initial Rolled* Initial Rolled* 600 rpm 5550 61 51 52 42 300 rpm 31 28 39 30 30 23 200 rpm 24 22 31 22 21 15 100rpm 15 14 21 14 15 10  6 rpm 6 5 9 5 6 4  3 rpm 5 4 8 4 5 3 PV, cp 24 2222 21 22 19 YP, lb/100 ft² 7 6 17 9 8 4 10-Second Gel 6 6 8 6 6 510-Minute Gel 9 7 10 6 6 5 Electrical 171 199 320 263 314 242 Stability,Volts Internal Phase 0.86 0.76 0.77 Water Activity HTHP Filtrate — 1.8 —2.0 — 0.8 at 250° F., mL est. Filtrate Water, Trace Nil Nil mL

[0103] One of skill in the art will appreciate that the fluids above maybe useful in drilling a wellbore.

EXAMPLE 3

[0104] The following illustrative embodiment of the present inventiondemonstrates the use of a bioreactor for the bioremediation of drillingcuttings.

[0105] Simulated drill cuttings thoroughly coated with Formulation Nwere slurrified and treated in the lab bioreactor at room temperature(25° C.). No nutrients were added and only moderate aeration was used.The level of retained fluid on cuttings (ROC) was initially about 11%w/w. A graphical representation of the exemplary results is shown inFIG. 2. Ecotoxicity data, with a loading rate on the test soil of 6% w/ware shown in Table 4 TABLE 4 Biodegradability, Toxicity & ElectricalConductivity of Formulations and Treated Cuttings 6% w/w Loading onTopsoil from Southern Alberta Grassland Biodegradability (65 days)Animal Toxicity Alfalfa Phytotoxicity* Relative % Loss of % % %Electrical Extractable Springtail Earthworm % Seed % Root ShootConductivity System Hydrocarbons Survival Survival Emergence ElongationMass (after 65 days) Formulation 98 80 100 100 149 97 1.0 A Formulation98 87 93 4 11 47 4.0 N Std. Diesel/ 68 0 0 3 8 25 4.9 CaCl₂/ BariteFormulation Formulation 99 90 100 100 108 105 0.8 A with BariteBioreactor- — 93 100 109 134 129 — Treated Cuttings, Form. NABioreactor- — 73 100 113 116 121 3.9 Treated Cuttings, Form. N

[0106] One skilled in the art may appreciate that the biodegradationprocess exhibits an induction period as the bacteria populationincreases. This may be manifested in the rapid increase of the OxygenUptake Rate (OUR). When the fuel (mud on the cuttings) depletes to anROC of about 3% w/w (after about 7 days), the rate of biodegradationpeaks and begins to fall rapidly. By 15 days, ROC has fallen to <1% w/w,and the rate has reached a plateau beyond which little reduction in ROCis observed. By contrast, a conventional diesel-based mud with CaCl₂brine internal phase exhibited a ROC of about 7% w/w even after 21 days.The phytotoxicity results indicate that both sets of cuttings, whenpre-treated in the bioreactor, may promote germination and growth ofalfalfa seeds. Bioreactor-treating cuttings appear to enhance thequality of the soil.

EXAMPLE 4

[0107] The following illustrative embodiment of the present inventiondemonstrates the use of a bioreactor for the bioremediation of drillcuttings from the field.

[0108] In a field trial, a C₁₂₋₁₃ LP-based drilling fluid was used todrill three intervals (16″ to 8½″) of a well in record time. The fluidhad OWR of 75/25 and was weighted up to 16 lb/gal with barite. Todetermine the suitability of direct land treatment of the drilledcuttings, a batch of the mud-laden cuttings from the shale shaker wassubjected to alfalfa seed germination tests. The cuttings weredetermined to have an initial loading of about 6% base fluid (ROC) bydry weight of cuttings. The 6-day long tests were run in triplicate with20 seedlings each, using 100% soil as a control and three ratios of %Soil/% Cuttings: 95/5, 75/25 and 50/50. Seedling survival rates (%Viability) and growth rates (% Length) are reported relative to thecuttings-free soil sample in Table 5. The statistical t-test probabilityfigures assume a two-tail distribution of the data; numbers less thanabout 0.05 are considered significant. The results indicate that thereis little or no effect of the cuttings on the health of the alfalfaseedlings until the % Soil/% Cuttings ratio reaches 50/50. Slightreductions in survival and growth rates for the cuttings-loaded soilsamples, though not highly significant (statistically), may be relatedto change in the soil texture, a condition which could be improved byaddition of sand and peat. TABLE 5 Untreated Field Cuttings from NewZealand Field Trial with Formulation N (with Barite) % Soil:% Cuttings95:5 75:25 50:50 Control Untreated Treated Untreated Treated UntreatedTreated Avg. Viability (%) 100 94 98 100 94 88 86 Avg. Plant Length (%)100 109 96 88 91 40 91 Probability that Deviation 1.0 0.62 .23 0.19 .080.00005 .08 from Control due to Chance

[0109] Alfalfa seed germination tests were conducted on thebioreactor-treated field cuttings. As shown in Table 5, pre-treatment ofthe cuttings in the bioreactor did not significantly affect theviability or growth rate in the 95/5 and 75/25 tests, but itsignificantly improved the growth rate of the seedlings for theproblematic 50/50 case. Thus, up to a loading of at least 75/25,pre-treatment of the cuttings is probably not necessary, whereas higherloadings may require the kind of pretreatment afforded by a bioreactor.

EXAMPLE 5

[0110] The following illustrative example of the present inventiondemonstrates the use of conventional thermal composting processes in thebioremediation of drilling cuttings.

[0111] Muddy drilled cuttings are mixed together with another solidorganic substance that is also reasonably readily degraded, e.g. strawor wood chips. This mixture is supplemented with nitrogen, phosphorousand other organic nutrients. Drill cuttings (Oxford Shale 5-10 mmdiameter) were coated with 10% w/w drilling fluid (Formulation N), 40%moisture content, and a carbon to nitrogen ratio of approximately 30:1.Naturally-occurring bacteria were used for these tests. Graphicalrepresentations of exemplary results are shown in FIG. 3. One of skillin the art will appreciate that the results show reduction in thehydrocarbon content of the composted cuttings over a period of 42 daysand show signs of the life cycle described earlier.

[0112] Vermi-composting: The fluids of the following illustrative andexemplary embodiments generate drill cuttings that were tested forbiodegradation using vermi-composting. The drilling fluids of thepresent invention were evaluated for their technical performance andthoroughly tested for drilling performance prior to environmentaltesting which included the following tests:

[0113] Alfalfa seed emergence and root elongation.

[0114] Earthworms (Esenia fetida) toxicity

[0115] Springtail (Folsomia candida) toxicity.

[0116] Microtox toxicity

[0117] Biodegradability (Respiration rate and hydrocarbon loss in moistsoil.)

[0118] The primary selection factor for the drilling fluid wasenhancement of production from tight gas sands, an additional criteriabeing the increased shale inhibition available from the use of syntheticfluids when compared to water-based fluids. This reduces the risk ofwell bore stability problems that had been experienced in previouswells. Additional benefits include increased rates of penetration andthe provision of fluid stability for high-pressure formations andsubsequent high-weight requirements.

EXAMPLE 6

[0119] The following illustrative example demonstrates the utility ofthe drilling fluids of the present invention in drilling subterraneanwells. A synthetic-based drilling fluid used employed a linear paraffinas the base fluid, calcium ammonium nitrate brine as the internal phase,eurisic diglyceride as the emulsifier and barite as the weightingmaterial. The fluid formulation is provided below in Table 6 in whichthe amounts are given in pounds per barrel (ppb). TABLE 6 FluidFormulation A B Base Oil Sasol C₁₂-C₁₃ paraffin, ppb 160.17 158.99Primary Emulsifier Novamul, ppb 8.00 8.00 Wetting Agent Versawet, ppb2.00 2.00 Fluid Loss Additive Novatec F, ppb 1.00 1.00 Rheology ModifierVersamod, ppb 1.00 2.00 Organophillic Clay VG-Plus, ppb 6.00 8.00Alkalinity Control Lime, ppb 6.00 6.00 Water Water, ppb 47.77 47.42Other NH₄Ca(NO₃)₃, ppb 32.30 31.96 Weight Material M-I Bar, ppb 239.87238.63

[0120] In the above formulation:

[0121] Sasol C₁₂-C₁₃ paraffin is a mixture of linear C₁₂₋₁₃ parafinavailable commercially from Sasol.

[0122] NOVAMUL is a emulsifing agent used with the NOVA PLUS systemavailable commercially from M-I LLC of Houston Tex.

[0123] VERSAWET is a wetting agent available commercially from M-I LLCof Houston Tex.

[0124] VERSAMOD is a LSRV agent available commercially from M-I LLC ofHouston Tex.

[0125] NOVATECH F is a fluid loss control agent available commerciallyfrom M-I LLC of Houston Tex.

[0126] VG-Plus is an organophilic clay viscosifying agent availablecommercially from M-I LLC of Houston, Tex.

[0127] MI Bar is a barite based weighting agent available commerciallyfrom M-I LLC of Houston, Tex.

[0128] Lime is commercially acceptable grade of calcium hydroxidecommonly available.

[0129] Calcium Ammonium Nitrate is a commercially acceptable gradecommonly a available.

[0130] The technical performance of the new fluid system was assessed inthe laboratory prior to use in the field. These tests were conductedsubstantially in accordance with the procedures in API Bulletin RP13B-2, 1990 which is incorporated herein by reference. The followingabbreviations may be used in describing the results of experimentation:

[0131] “E.S.” is electrical stability of the emulsion as measured by thetest described in Composition and Properties of Drilling and CompletionFluids, 5th Edition, H. C. H. Darley, George R. Gray, Gulf PublishingCompany, 1988, pp. 116, the contents of which are hereby incorporated byreference. Generally, the higher the number, the more stable theemulsion.

[0132] “PV” is plastic viscosity that is one variable used in thecalculation of viscosity characteristics of a drilling fluid, measuredin centipoise (cP) units.

[0133] “YP” is yield point that is another variable used in thecalculation of viscosity characteristics of drilling fluids, measured inpounds per 100 square feet (lb/100 ft²).

[0134] “AV” is apparent viscosity that is another variable used in thecalculation of viscosity characteristic of drilling fluid, measured incentipoise (cP) units.

[0135] “GELS” is a measure of the suspending characteristics, or thethixotropic properties of a drilling fluid, measured in pounds per 100square feet (lb/100 ft²).

[0136] “API F.L.” is the term used for API filtrate loss in milliliters(ml).

[0137] “HTHP” is the term used for high temperature high pressure fluidloss at 200° F., measured in milliliters (ml) according to API bulletinRP 13 B-2, 1990.

[0138] The initial properties of the fluid were measured and then thefluid was aged at 250° F. for 16 hours with rolling. The rheology of theinitial fluid and the aged fluid were measured at 120° F. Representativedata is given below in Table 7: TABLE 7 Fluid A Fluid B Fluid PropertiesInitial Aged Initial Aged Mud Weight (SG) 1.44 1.44 1.44 1.44 600 rpmRheology 44 41 55 54 300 rpm Rheology 29 26 35 33 200 rpm Rheology 19 1927 25 100 rpm Rheology 14 12 19 16 6 rpm Rheology 6 5 10 7 3 rpmRheology 6 5 9 7 PV., cP 15 15 20 21 YP, lb/100 Ft² 14 11 15 12 10 s.Gel, lb/100 ft² 8 7 14 11 10 min, Gel, lb/100 t² 11 11 19 20 HTHP @ 250°F., cc/30 2.4 2.0 2.8 2.4 ES @ 120° F., Volts 658 210 795 422

[0139] Upon review of the above data, one of ordinary skill in the artshould appreciate that the above formulated fluid is useful as anoleaginous drilling fluid.

[0140] The fluid was introduced in a field where high weight water-basedmuds from 16-19 lb/gal were traditionally used at depths from around1000 m with hole problems experienced, including but not limited to:extremely reactive plasticene clays, squeezing up the inside of thecasing; formation of “mud rings”; significant borehole ballooning; highbackground gas and gas kicks; numerous hole packoffs due to tectonics,e.g. 3-4-in. pieces of wellbore popping off into the annulus; minimalhole tolerance to formation pressure balance, i.e. a fine line betweengains and losses; fluid rheology problems at high weights; inducedfractures due to ECD's; water flows; no logs successfully run;difficulty in running casing; and/or resultant fluid cost contributed to30% of the AFE Total well budget.

[0141] Eleven wells had been drilled in the area with water-based mudand all experienced extensive hole problems. Alternative systems wereconsidered and the newly engineered “bioremediation friendly” drillingfluid of the present invention was chosen based on the selectioncriteria discussed previously.

[0142] Well 1 was drilled using a prior art silicate-based system andresulted in three stuck pipe incidents, two sidetracks, significanttorque and overpull, ballooning from plastic clays, numerous packoffs,high rheologies due to excessive MBTs, and difficult wiper trips. Thewell never reached total depth and had to be plugged and abandoned dueto poor hole conditions. It took 28 days to drill to 1150 m.

[0143] Well 2 was drilled with a drilling fluid formulated according tothe teachings of the present invention as noted above. The resultssurpassed reasonable expectations of performance by one of skill in theart. A depth of 2544 m was achieved in only 34 days. No drillingproblems were experienced and torque and drag was reduced. The hole wassuccessfully logged with the caliper indicating gauge hole, and holeintegrity was maintained during a five-day, open-hole testing program.This had not been achieved in previous wells and was unexpected andsurprising.

[0144] Additional wells have since been drilled in this area using thesame fluid and with minimal hole problems and cheaper overall drillingfluid costs compared to the previous water-based muds wells. Thepaleontology results are the best the operator has seen and all holeshave reached total depth with efficient casing runs and logging. Holeconditions are still difficult but the combination of experience; gooddrilling practice and the “bioremediation friendly” synthetic mud systemhas contributed to a successful ongoing drilling program. Skinirritation levels are very low by comparison with other synthetic andoil-based systems that have been used in other countries. However,strict adherence to a good occupational hygiene program includingbarrier cream, nitrile gloves and disposable coveralls greatly reducesthe chances of irritations. The resulting drill cuttings were mixed withsawdust and/or wood shavings (45% w/w) at the rig site to facilitatetransport and then delivered for bioremediation.

EXAMPLE 7

[0145] The present illustrative example demonstrates the utility ofusing the drilling fluids of the present invention in drillingsubterranean wells. An advantage of this illustrative example was thefact that the fluid was used in an 8½-in. sidetrack of a wellbore,originally drilled with a potassium chloride/Glycol water-based mud,thus permitting direct comparison of conditions and performance.

[0146] According to prior field practice, drilling fluid weights forwells in this area are 9.2-11 pounds/gallon (lb/gal.) using highlyinhibitive water-based muds. Although hole problems were generally lessin this area compared to the area drilled in the Example A, there werestill significant challenges that were difficult to overcome using theprior practice including: highly reactive, tectonically stressed shalebands, causing excessive cavings; interbedded clays dispersing into thesystem and creating concerns with rheology; slow rate of penetrationthrough the lower section of the hole; considerable borehole breakoutdue to openhole exposure time; seepage losses to limestone; coalstringers; excessive trip times due to reaming and back reaming of openhole sectioning.

[0147] Using a prior art water-based drilling mud, an 8½-in. hole wasdrilled in 47 days using a water-based mud, including a four-day fishingrun, with a section length of 3005 m. Average rate of penetrationthrough the lower section of the hole was 2-4 m/hr. Hole washout wasextensive and difficult trips were experienced. The logs could not berun to the bottom. The high MBT of the system required increaseddilution requirements.

[0148] After plugging back the well and displacing to the fluids of thepresent invention, the hole was drilled ahead. A synthetic-baseddrilling fluid was used and employed a linear paraffin as the basefluid, calcium ammonium nitrate brine as the internal phase, and bariteas the weighting material. The fluid formulation is provided in theprevious example.

[0149] Drilling was fast and 22 days into drilling, the depth wasgreater than that of the original well, reducing 26 days off theprevious time curve. By day 25, the well had reached a depth of 4800 mwith no hole problems experienced, minimal overpull and drag, and nologging or tripping incidents. The logs revealed an in-gauge hole. Thedrilling mud formulation and fluid system was stable. The cuttings werecollected in a direct collection bin at the base of the auger outlet andtransferred to a truck after blending with bulking material (sawdustand/or wood shavings) to facilitate transport. The resultant reductionin rig downtime considerably offset the costs incurred by using thedrilling fluids of the present invention. The resulting drill cuttingswere mixed with sawdust and/or wood shavings (45% w/w) at the rig siteto facilitate transport and then delivered for bioremediation.

EXAMPLE 8

[0150] Vermicomposting of Drill Cuttings

[0151] The following illustrative test examples demonstrate thefeasibility of utilizing vermicomposting for the bioremediation ofdrilling cuttings. Drill cuttings were recovered in a routine mannerfrom the drilling of above noted test wells. Components of the drillingfluid have been previously discussed above.

[0152] First Test: This first test was conducted to determine theviability of vermicomposting for the bioremediation of drillingcuttings. The drill cuttings were mixed with sawdust and/or woodshavings (45% w/w) or other similar cellulose based material tofacilitate transport and then delivered to the vermiculture site wherethey were blended with paunch waste from a slaughter house before beingfed to the worm beds. The mixture of drill cuttings, saw dust and paunchwaste is formulated to ensure that the correct proportion of carbon,nutrients and moisture are present. This blending step is an importantprecursory step in the vermicast production as the quality of the“feedstock” ultimately impacts upon the potential for optimal conditionsto exist during the resultant vermicasting process. Because thebio-remediation of the mixture is an aerobic process, the optimumconditions for worm driven waste management of these materials is 75%(w/w) moisture, with a carbon nitrogen ratio of 25:1

[0153] Once the blended material has been prepared it is loaded into awatertight wagon for application as “feedstock” for the worms to processin mounds referred to as “windrows”. Each of these windrows isapproximately 88 meters long by approximately 3 meters wide. There areapproximately two meters wide access tracks between each of the windrowsfor access of the feed-out wagon to apply the mixed material, and alsoto allow for ongoing maintenance of the windrows and the subsequentvermiculture production processes.

[0154] The blended material is applied to the center/top of windrows,typically at an average depth of 15-30 mm on a weekly basis. The exactapplication rate depending upon climatic conditions. Generally theapplication rate was higher in summer than winter. The worms work thetop 100 mm of each windrow, consuming the applied material over a fiveto seven-day period.

[0155] The windrows are aerated prior to each feeding procedure ensuringaerobic conditions within all of the beds. This aerator is attached tothe linkage on the tractor and side arms guide any material (vermicast)back onto the beds ensuring no windrow exceeds the width to be coveredby the covers themselves

[0156] Each of the windrows is covered with a windrow cover, preferablya fiber mat with polypropylene backing. The covering allows for thenecessary exclusion of light and avoids excessive wetting conditionsoccurring within the windrow, thus assisting in maintaining an optimallycontrolled environment in which the worms produce their castings.Controlled irrigation systems are periodically used on each the windrowsto keep the covers moist to maintain a damp but not “wet” environment.The covering should be secured to prevent the cover from being removedby the elements. For example, each side of the preferredpolypropylene/fiber matting is fitted with a D12 steel rod to act as aweight to stop wind lifting the covers off the bed.

[0157] Consumption rates can vary and are 100% of the worms bodyweight/day in the seasons of spring and autumn and 40% during theextremes of winter and summer. As a result, the volume and feedapplication rates and other important potential variables including thetemperature, moisture content, pH, population dynamics, aerobicmaintenance, and vermicast extraction techniques, are each required tobe carefully monitored and varied accordingly. One of skill in the artof vermicomposting and vermiculture should be able to systematicallyvary each of these parameters in order to optimize the conditions withinany particular windrow to maximize the bio-remediation process.

[0158] First Test Sampling and Analytical Procedures: 50-cc Grab sampleswere taken at time zero and then at approximately weekly intervalsthroughout the course of the test. Samples were transported by overnightcourier to the analytical laboratory where they were stored at 4° C.prior to analysis. Tests for total petroleum hydrocarbons contentaccording to the New Zealand Oil Industries Environmental Working Group(OIEWG) guidelines and recommendations.

[0159] Once in the laboratory the samples were ground with dry ice(Cryogrinding) prior to sub-sampling and subsequent analysis. Samplesfor total petroleum hydrocarbons determination were extracted usingdichloromethane and sonication. The extracted samples were then driedwith silica prior to analysis by GC-FID the detection limit of theprocedure used by the laboratory being 60 mg/kg.

[0160] Data that is exemplary of the results of this study is presentedbelow in Table 8 TABLE 8 Hydrocarbon content (GC-FID) (OIEWG carbonbands; mg/kg dry wt.) Cuttings + Sawdust 0 4 10 13 19 21 28 Days C₇-C₉<600 <80 <50 <8 <7 <7 <20 <20 C₁₀-C₁₄ 41300 4600 2700 140 127 82 <30 <40C₁₅-C₃₆ <2000 <300 <200 <30 40 <30 <60 <80 Total 41000 4600 2700 150 170110 <100 <100

[0161] The data from Table 8 for the total hydrocarbon content is showngraphically in FIG. 4.

[0162] First Test Results: In the first test the hydrocarbonconcentrations decreased from 4600 mg /kg (dry wt) to less than 100mg/kg (dry wt) in under 28 days with less than 200 mg/kg (dry wt)remaining after 10 days in what appears to be a fairly typicalexponential type degradation curve FIG. 4.

[0163] The bulk of the hydrocarbons detected comprised C₁₀-C₁₄ aliphatichydrocarbons which is in good agreement with the carbon chain lengthdistribution of the C₁₂-C₁₇ linear paraffin blend used in this drillingfluid and indicates that there were no external sources of contaminatinghydrocarbons.

[0164] There was no detectable excess mortality amongst the worms thatthe drill cuttings were fed to and although the numbers were notquantified, there appeared to be a definite preference among the wormsfor the area where the cuttings and paunch feed had been applied. It isnot clear if this was due to the hydrocarbons attracting the worms orthe increased availability of easily assimilated organiccarbon/microbial biomass that would be associated with the highlybiodegradable linear paraffins of the drill cuttings.

[0165] It was also noted that there was complete physical degradation ofthe cuttings by the vermidigestion process and none of the originalintact cuttings could be found, the original cuttings size being 5-10 mmin diameter.

[0166] Upon review of the above data, one of ordinary skill in the artof bio-remediation should understand and appreciate that thevermicomposting process of the present invention has substantiallyreduced the hydrocarbon content of the drill cuttings.

[0167] Second Test: In this second test, variable amounts of drillingcuttings were mixed with the rumen material so as to determine the mostsuitable conditions for vermicomposting of drilling cuttings. Thedrilling cuttings utilized were conventionally recovered from the testwells noted above and processed to form vermicultre feed mixtures. Thevarying mixtures were applied to the windrows during vermiculture siteslocal Summer time as indicated below in Table 9. TABLE 9 Experimentaldesign summary Description Treatment 1 Bed #4 Control, no drillcuttings, Paunch only Treatment 2 Bed #2 30:70 (w/w) drill cuttings:paunch material Treatment 3 Bed #3 50:50 (w/w) drill cuttings: paunchmaterial Treatment 4 Bed #5 70:30 (w/w) drill cuttings: paunch materialTreatment 5 Bed #1 100% drill cuttings; no paunch

[0168] Drill cuttings were mixed with sawdust (45% w/w) to facilitatetransport and then delivered to the vermiculture site. At thevermiculture site the drill cuttings mixed with sawdust was blended withpaunch waste (undigested grass) from a slaughterhouse before being fedto the worm beds using an agricultural feed-out wagon of the sort usedfor feeding silage to livestock.

[0169] Successful degradation of organic materials by worms was obtainedby providing optimum environmental conditions for the worms, including acarbon nitrogen ratio (25:1) and moisture content (75%). The drillcuttings were blended and mixed with the paunch material at variableratios and then combined with water giving a 50:50 v/v water: solidsslurry that could be evenly distributed from the feedout wagon. Blendingand mixing of the drill cuttings, paunch wastes, green wastes and waterwas performed on a bunded concrete pad that is approximately 30 m by 15m in diameter, giving 450 m² for controlled waste mixing and was carriedout in a Marmix combined mixing and feedout wagon, the three internalaugers of the trailer being used to ensure thorough mixing.

[0170] Once the blended material had been prepared it was loaded into awatertight “feed out” wagon for application as “feedstock” for the wormsto process in mounds referred to as “windrows”. The windrows were 88 min length by 3 m wide. There are two meter-wide access tracks betweeneach of the windrows for access of the feed-out wagon to apply the mixedmaterial, and also to allow for ongoing maintenance of the windrows andthe subsequent vermiculture production processes.

[0171] The blended material was applied to the center/top of thewindrows, usually once a week at an average depth of 15-30 mm. The exactapplication rate depends upon climatic conditions and is higher insummer than winter. The worms “work” the top 100 mm of each windrow,consuming the applied material over a five to seven-day period. Once thetest materials had been applied the worm beds were fed on a weekly basiswith unamended paunch material as part of the normal worm driven wastemanagement routine carried out at the site.

[0172] Each of the windrows was covered completely by apolypropylene-backed felt mat which excludes light from the worm bedand, although semi permeable to water, the polypropylene backingdeflects heavy rainfall away from the surface of the bed and preventsthe windrow from becoming waterlogged. This preferred practice maintainsan optimum aerobic environment the worms to work in.

[0173] The windrows were also fitted with a controlled irrigation systemthat could be used to keep the covers moist and maintain the correctmoisture content during periods of low rainfall.

[0174] As the use of worms for degradation of the mixture is an aerobicprocess the windrows are aerated prior to each feeding procedure toensure aerobic conditions within all of the beds and maintain optimumconditions for the worms and their associated microbial processes. Theaerator is attached to the power take-off linkage on the tractor andside arms guide any material (vermicast) back onto the beds, ensuring nowindrow exceeds the width to be covered by the felt mat.

[0175] Once the worms had degraded the waste and converted the appliedmaterial into vermicastings (worm castings), the vermicast organicfertilizer was harvested using an industrial digger and was thenpackaged for distribution and use on agricultural and horticultural landas a beneficial fertilizer and soil conditioner.

[0176] Second Test Sampling and Analytical Procedures: Triplicate coresamples were taken randomly and on an approximately weekly basis from a(6 m×3 m) sub section of each of the 5 research windrows using 60 mmdiameter plastic core tubes. The core tubes were “screwed” all the wayto the base of the windrow to ensured the sample contained anyhydrocarbon material that might have migrated vertically down throughthe windrow, either as a result of leaching or mechanical or biologicalmovement and transport.

[0177] All samples were analysed for total petroleum hydrocarbonscontent with more detailed soil chemistry and heavy metal analysis beingperformed on the time zero and 60-day (termination) samples to study theeffect of the process on nutrient and heavy metal concentrations.Seasonal variations in temperature were recorded, as they are climaticfactors that could influence rates of hydrocarbon degradation in theworm beds.

[0178] The following Table 10 gives a summarized description of themethods used to conduct the analyses in this illustrative example. Thedetection limits given below are those attainable in a relatively cleanmatrix. Detection limits may be higher for individual samples shouldinsufficient sample be available, or if the matrix requires thatdilutions be performed during analysis. TABLE 10 Parameter Method UsedDetection Limit pH 1:2 water extraction of dried sample. 0.1 pH Units pHread directly. Electrical 1:2 water extraction of dried sample. 0.05mS/cm in Conductivity Measured conductivity at 25° C. extract (EC)Soluble Salts* Calculation: measured EC (mS/cm) × 0.02 g/100 g 0.35.Total Determined by Dumas combustion 0.02 g/100 g Nitrogen* procedureusing Elementar dry wt VarioMAX instrument. Total Carbon* Determined byDumas combustion 0.05 g/100 g procedure using Elementar dry wt VarioMAXinstrument. Zinc Nitric/hydrochloric acid digestion. 0.1 mg/kg ICP-MSdetermination. dry wt Copper Nitric/hydrochloric acid digestion. 0.05mg/kg ICP-MS determination. dry wt Ammonium-N* 1:2 water extraction ondried sample. 0.1 mg/L in FIA colorimetric determination, extractNitrate-N 1:2 water extraction on dried sample. 0.2 mg/L in FIAcolorimetric determination, extract Nitrite-N 1:2 water extraction ondried sample. 0.02 mg/L in FIA colorimetric determination, extractPhosphate-P 1:2 water extraction on dried sample. 0.04 mg/L in FIAcolorimetric determination, extract Arsenic Nitric/hydrochloric aciddigestion. 0.1 mg/kg ICP-MS determination. dry wt MercuryNitric/hydrochloric acid digestion. 0.01 mg/kg ICP-MS determination. drywt Barium Nitric/hydrochloric acid digestion. 0.01 mg/kg ICP-MSdetermination. dry wt Cadmium Nitric/hydrochloric acid digestion. 0.005mg/kg ICP-MS determination. dry wt Chromium Nitric/hydrochloric aciddigestion. 0.1 mg/kg ICP-MS determination. dry wt NickelNitric/hydrochloric acid digestion. 0.1 mg/kg ICP-MS determination. drywt Lead Nitric/hydrochloric acid digestion. 0.03 mg/kg ICP-MSdetermination. dry wt

[0179] All samples were analyzed for total petroleum hydrocarbonscontent with more detailed soil chemistry and heavy metal analysis beingperformed on the time zero and termination samples to study the effectof the process on nutrient and heavy metal concentrations. Seasonalvariations in temperature were also recorded.

[0180] Second Test Results: There was no visual mortality among thetreated earth worms and the hydrocarbon “fingerprint” matched theapplied base fluid. It was also apparent that the applied drill cuttingsmix caused the worms to actively seek out the clumps on materialcontaining drill cuttings.

[0181] Total petroleum hydrocarbons: From the results shown in FIG. 5 itcan be seen that the background hydrocarbon samples were around thedetection levels for the method for the duration of the test indicatingthat there were no significant external sources of hydrocarbons beingadded to the worm beds apart from the test material

[0182] Due to the heterogeneous manner in which the cuttings wereapplied to the worm bed some of the initial samples taken were veryvariable and this is reflected in the total petroleum hydrocarbonsresults shown in FIGS. 5, 6, 7, 8 and 9 However taken overall (FIG. 10)a number of general trends can be seen. The hydrocarbons in the cuttingsapplied at 30% w/w decreased from an average of 1900 mg/kg to less than60 mg/kg within 45 days. The hydrocarbons in the cuttings applied at 50%w/w decreased from an average of 2100 mg/kg to the detection limitwithin 45 days but then showed a slight increase for some, unknownreason, although it may be related to the heterogeneity of the worm bedand sampling variation.

[0183] The hydrocarbons in the cuttings applied at 70% w/w showed quitea clear trend and decreased from an average of 20,000 mg/kg to 1500mg/kg within 45 days but there was no subsequent reduction in thehydrocarbon concentration after this time. After the initial degradationit was found that the clumps of cuttings and feed mixture within theworm bed had dried out and become compacted making them unpalatable tothe worms. This suggests that, as the worms are not breaking down thecuttings, that the degradation is no longer worm driven but purelymicrobial and this is not expected to be particularly fast given theunfavorable conditions and lack of moisture within the cutting/feed mixclumps. This also means that as the worm beds were regularly fed withunammended paunch material that the cuttings will move out of the wormsfeeding zone further reducing the rate of degradation

[0184] The hydrocarbons in the cuttings applied at 100% w/w (without anypaunch amendments) did not show any obvious degradation throughout thecourse of the test (60 days). It is thought that this is because theconsistency of the cuttings (mixed with sawdust to facilitate transport)combined with that lack of paunch material (which constitutes a largepart of the worm “normal” diet) makes the cuttings very “unappealing” tothe worms and prevents the worms from degrading the material

[0185] Overall the rates of hydrocarbon degradation were slower in thesecond test than in the first and this is thought to be due to theprevailing weather and climatic conditions.

[0186] The importance of the worms in enhancing the rates of hydrocarbondegradation is shown by the much slower rates of decrease in hydrocarbonconcentration in samples of cuttings blended with paunch material thatwere in parts of the windrow that were inaccessible to the worms andwere not tilled and aerated

[0187] Soil Chemistry: Looking at the pH data shown in FIG. 11 it can beseen that there is slight increase in pH as more cuttings are applied tothe worm bed and that the pH tends to be slightly higher at the end ofthe experiment. This would be caused by the slightly alkaline nature ofthe drill cuttings and base fluid and the release of the lime from thedrilling fluid emulsion as it is broken down. The increase in pH is notsufficiently high the adversely affect the earth worms.

[0188] The remaining soil chemistry results are given in FIGS. 12 to 17.Electrical conductivity is a measure of the total salt or ion contentwithin the sample and can have significant effects of soil propertiessuch as the cation exchange capacity etc. At time zero the electricalconductivity can be seen to generally increase (see FIG. 12) as morecuttings are applied. This probably reflects the use of calcium ammoniumnitrate in the brine phase of the drilling fluid, the more cuttingsadded the higher the electrical conductivity. At the end of the test theelectrical conductivity is constant for all the windrows to which drillcuttings were added, suggesting that if this is the case, that eitherthe bacteria have utilized the calcium ammonium nitrate or theearthworms involved in the remediation process. This is confirmed by theother soil chemistry data for nitrogen containing materials (see FIGS.14, 15, 16). It is not clear why the electrical conductivity in thecontrol (no added drill cuttings) should differ at the start and finishof the test as these would be expected to be the same unless the wormdriven waste management process results in the mobilization of salts,which are subsequently re-used at a faster rate in the treated worm bedsand which are assumed to have a more dynamic microbial populationbecause of the presence of the readily biodegradable linear paraffins.

[0189] As mentioned previously the nitrogen and phosphorous containingcompounds when taken overall one of ordinary skill in the art shouldconclude that the concentration of these elements, which are essentialfor microbial degradation and growth decrease over the course of thetest as they are used up by the bacteria involved in the degradationprocess and converted into microbial and earth worm biomass.

[0190] Heavy Metals: The barium concentrations shown in FIG. 18 wereused as a conservative marker to ensure that the hydrocarbons were beingdegraded within the cuttings pile and that there was no loss of thecuttings through physical removal. Looking at the results one of skillin the art should see that as more cuttings are added to the worm bed,the barium concentration increases. It is however, interesting to notethat the barium concentration in the highest application rate is lowerat the end of the test than at the start. Currently we do not have anexplanation for this phenomenon but it is interesting to note that thedecrease in barium concentration occurred in the windrow with the leastmicrobial and earth worm degradation of the drill cuttings (100% w/wapplication with no added paunch material) suggesting that it could belinked to bioaccumulation of the metal.

[0191] Heavy metal bioaccumulation: As earthworms are known toaccumulate heavy metals within their tissues, samples of earth wormswere analyzed for heavy metal content at the end of the experiment.Looking at the results shown in FIG. 19 it can be seen that while mostof the metal concentrations remain fairly constant at the differentcuttings application rates, there is a slight increase in the leadconcentration within the earth worm's tissues coupled with a moreobvious increase in the barium concentration in the 30%, 50% and & 70%w/w additions. It is interesting to note that the barium and lead levelsshow a slight decrease at highest rate of addition (where there was verylittle biological “working” of the cuttings), presumably because theworms were not ingesting the cuttings in large amounts therefore therewas less bioaccumulation. This reduced rate of activity in the 100%addition may also explain some of the other variations in nutrientlevels etc

[0192] Third Test: The third test was conducted utilizing 30% and 50%w/w drill cuttings mixture were repeated during local Winter time at thevermiculture facility. The same methods described above in the previsouswere utilized.

[0193] Third Test Sampling and Analytical Procedures: Initially six coresamples were taken from each of the treatment areas (total sample weightapproximately 1 KG), and combined together at the test site in largemixing container where they were thoroughly mixed prior to sub-samplinga 250-300 gm composite sample, which was subsequently sent for analysis.After five days the number of core samples was reduced to four but themixing and sub-sampling procedure remained the same.

[0194] Third Test Results: Upon review of the results of the presenttest, one of skill in the art should understand and appreciate that theclimatic conditions for the winter test (Test2) did not favor maximumrates of degradation in the worm beds and the sample variability neededto be reduced. Thus it was decided to repeat the test a third time undermore favorable environmental conditions using a modified samplingprocedure as discussed above.

[0195] Again there was no visual mortality of the worms and theyappeared to actively seek out the clumps of drill cuttings.

[0196] Total Petroleum Hydrocarbons: As in previous experiments nosignificant amounts of hydrocarbons were found in the windrows that didnot have cuttings applied (see FIG. 20) while the 30 and 50% applicationrates showed significant degradation of hydrocarbons to backgroundlevels within 30 days. The initial results for the cuttings applied at30% w/w are somewhat erroneous due to incorrect analytical proceduresbeing used for these samples resulting in the loss of some of thevolatile hydrocarbon fractions. However, one of skill in the art willnotice that a clear decrease in hydrocarbon concentration can still beseen.

[0197] Soil Chemistry: The soil chemistry parameters for the third testwere also somewhat inconclusive although there did appear to be similartrends to those observed in the second test, i.e. a general decrease inthe nitrogen and phosphorous containing compounds as they are used up inthe microbial degradation process.

[0198] Heavy Metals: As in the second test barium concentrations in thesamples increased when drill cuttings were applied, but the limitednumber of samples analyzed for barium at the start and finish of thetest make it difficult to draw any firm conclusions.

[0199] The worms did show an increase in a number of heavy metals afterfeeding on material containing drill cuttings and barite weightingmaterial but it is not clear if the heavy metals were found in theworm's gut or tissues even though the worms were fasted for 24 hoursbefore sampling. This length of time might not be long enough to purgethe gut contents, but as this is an important question it is intended tobe the subject of further studies aimed at better understanding thedegradation process and bioaccumulation or change in the bioavailabilityof the heavy metals.

[0200] The results of the above series of tests should indicate to oneof ordinary skill in the art that under suitable conditions there issubstantial degradation of the hydrocarbons within the worm bed. Factorssuch as temperature effect rates of hydrocarbon degradation. Goodhusbandry of the worms appears to be important to the success of theprocess and this is shown by the use of a 30-50% cuttings addition. Anyhigher and the cuttings and hydrocarbons are less available to the wormsor are unpalatable (100% w/w) and are not degraded. Cuttings which areunpalatable to the worms will eventually become buried in the worm castas more food is applied to the worms beds and move out of the feedingzone, meaning that the degradation is no longer worm driven. Uponconsideration and review by one of ordinary skill in the art, optimumbenefit is obtained from the synergistic use of drilling fluids designedfor bioremediation and vermiculture technology, the worms being used toadd value to the cleaned cuttings and further reducing disposal costs.

[0201] In view of the above disclosure and examples, one of ordinaryskill in the art should appreciate that one illustrative embodiment ofthe present invention includes a biodegradable wellbore fluid, suitablefor drilling subterranean wells, with an oleaginous phase including alinear paraffin having 11-18 carbon atoms, a non-oleaginous phasecontaining a salt of a biodegradable anion, and an emulsifying agent ina concentration capable of forming an oleaginous fluid suitable for useas a drilling fluid. A weighting agent, fluid-loss reducing agent, andviscosifying agent may also be present. The oleaginous phase maycomprise from about 30 to 99% by volume of the wellbore fluid, and thenon-oleaginous phase may comprise from about 1% to about 70% by volumeoff the wellbore fluid. The non-oleaginous phase may be selected fromfresh water, a brine containing organic or inorganic dissolved salts, aliquid containing water-miscible organic compounds, or combinationsthereof. The emulsifying agent is preferably an eurisic diglyceride orother chemically similar compounds. The weighting agent may be selectedfrom calcium carbonate, hematite, ilmenite, barite, mullite, gallena,magnanese oxides, iron oxides and combinations thereof. The viscosifyingagent may be an organophilic clay.

[0202] One of skill in the art should appreciate that anotherillustrative embodiment of the present invention includes a method ofproducing a biodegradable wellbore fluid by blending an oleaginous phasewith a linear paraffin having 11-18 carbon atoms, a non-oleaginous phasecontaining a salt of a biodegradable anion and substantially free ofhalogen ions, and an emulsifying agent in a concentration capable offorming an oleaginous suitable for use as a drilling fluid.

[0203] A further illustrative embodiment of the present inventioninvolves drilling a subterranean well by attaching a cutting bit to alength of drill pipe, rotating the cutting bit, and removing cuttingsfrom around the bit with a drilling fluid which is a biodegradablefluid. This fluid contains an oleaginous phase with a linear paraffinhaving 11-18 carbon atoms, a non-oleaginous phase containing a salt of abiodegradable anion, and an emulsifying agent in a concentration capableof forming an oleaginous suitable for use as a drilling fluid. Thecuttings removed from the well may be bioremediated using, land farming,conventional composting, a bioreactor or by vermi-composting.

[0204] Another illustrative embodiment of the present invention is amethod of bio-remediation involving the drilling of a subterranean wellwith a fluid containing an oleaginous phase with a linear paraffinhaving 11-18 carbon atoms, a non-oleaginous phase containing a salt of abiodegradable anion and substantially free of halogen ions, and anemulsifying agent in a concentration capable of forming an oleaginousfluid suitable for use as a drilling fluid. The cuttings are removedfrom the well, transported to a remediation site, and blended withnutrients to create a treatment feed. This treatment feed is spread onland for composting, or placed in a bioreactor for bacteria to performthe remediation. The treatment feed may also be pretreated in abioreactor or compost vessel before it is spread on land.

[0205] Additionally, one of skill in the art should recognize thatanother illustrative embodiment of the present invention involves a soilamendment made from cuttings from a wellbore which was drilled using afluid of the present invention and sawdust, wood shavings, paunch wasteor mixtures thereof. The soil amendment may be created by drilling asubterranean well with a drilling fluid containing an oleaginous phasewith a linear paraffin having 11-18 carbon atoms, a non-oleaginous phasecontaining a salt of a biodegradable anion, and an emulsifying agent ina concentration capable of forming an oleaginous fluid suitable for useas a drilling fluid. The cuttings are removed from the well andtransported to a remediation site where nutrients are blended in tocreate a treatment feed. The treatment feed is spread on a land-farmwhere bacteria perform the remediation. The treatment feed may bepretreated in a bioreactor or composting vessel prior to landremediation.

[0206] In further view of the above disclosure, one of ordinary skill inthe art should understand and appreciate that one illustrativeembodiment of the present invention includes a method of biodegradingdrilling cuttings coated with a drilling fluid by vermicomposting. Thedrilling fluid formulation utilized in such an illustrative methodincludes a linear paraffin having 11-18 carbon atoms, a non-oleaginousphase, and an emulsifying agent. The drilling fluid is formulated suchthat it is biocompatible with vermicomposting. In one illustrativeembodiment, the method includes mixing the drilling cuttings with acompostable waste material so as to provide a compostable balance ofnitrogen and carbon content. Within one such illustrative embodiment thenitrogen and carbon content have a ratio of about 2:1 to about 100:1 andmore preferably the nitrogen and carbon content has a ratio of about25:1. In one embodiment of the present invention, the vermicomposting iscarried out in a bioreactor and in such instances the vermiculturebioreactor is selected from a bin vermicomposter, a rotating drumvermicomposter, windrows, covered windrows and combinations of these.The drilling fluid utilized in the above noted illustrative embodimentshould be formulated such that it is useful in the drilling ofsubterranean wells. In one such instance the drilling fluid includes aweighting agent, a fluid loss control agent and/or similar suchcompounds typically utilized in the formulation of drilling fluids. Ofimportance is that such alternative components of the drilling fluidshould not substantially harm the biocompatability of the drill cuttingswith vermiculture. Likewise, the non-oleaginous fluid utilized in theabove illustrative embodiment should not substantially harm thebiocompatability of the drill cuttings with vermiculture. In onepreferably illustrative embodiment, the non-oleaginous fluid is selectedfrom fresh water, sea water, a brine containing organic or inorganicdissolved salts, a liquid containing water-miscible organic compounds,combinations of these and similar compounds. As previously noted, theemulsifying agent utilized in the formulation of the drilling fluidsused in the above noted illustrative embodiments can be selected from awide range of suitable emulsifying agents. However, such selection ismade such that the emulsifying agent is does not substantially harm thebiocompatability of the drill cuttings with vermiculture. One suchpreferred emulsifying agent is an eurisic diglyceride.

[0207] The present invention also includes a method for biodegradingdrilling cuttings coated with a drilling fluid. One such illustrativemethod that should be apparent to one of ordinary skill in the art is amethod including exposing the drilling cuttings to a vermicompostingenvironment for a sufficient period of time to permit the worms tobiodegrade the organic components of the drilling fluid. Within such anillustrative method the drilling fluid is formulated to include linearparaffin having 11-18 carbon atoms, a non-oleaginous phase, and anemulsifying agent. In one illustrative embodiment, the method includesmixing the drilling cuttings with a compostable waste material so as toprovide a compostable balance of nitrogen and carbon content. Within onesuch illustrative embodiment the nitrogen and carbon content have aratio of about 2:1 to about 100:1 and more preferably the nitrogen andcarbon content has a ratio of about 25:1. In one embodiment of thepresent invention, the vermicomposting is carried out in a bioreactorand in such instances the vermiculture bioreactor is selected from a binvermicomposter, a rotating drum vermicomposter, windrows andcombinations of these. The drilling fluid utilized in the above notedillustrative embodiment should be formulated such that it is useful inthe drilling of subterranean wells. In one such instance the drillingfluid includes a weighting agent, a fluid loss control agent and/orsimilar such compounds typically utilized in the formulation of drillingfluids. Of importance is that such alternative components of thedrilling fluid should not substantially harm the biocompatability of thedrill cuttings with vermiculture. Likewise, the non-oleaginous fluidutilized in the above illustrative embodiment should not substantiallyharm the biocompatability of the drill cuttings with vermiculture. Inone preferably illustrative embodiment, the non-oleaginous fluid isselected from fresh water, sea water, a brine containing organic orinorganic dissolved salts, a liquid containing water-miscible organiccompounds, combinations of these and similar compounds. As previouslynoted, the emulsifying agent utilized in the formulation of the drillingfluids used in the above noted illustrative embodiments can be selectedfrom a wide range of suitable emulsifying agents. However, suchselection is made such that the emulsifying agent is does notsubstantially harm the biocompatability of the drill cuttings withvermiculture. One such preferred emulsifying agent is an eurisicdiglyceride.

[0208] The present invention also includes a method of vermicularbio-remediation of oil contaminated solids. One such illustrativeembodiment includes a method including providing the oil contaminatedsolids to a vermicular bioreactor, and allowing the worms within thevermicular bioreactor to biodegrade the oil contaminated solids. Thedrilling fluid is formulated such that it is biocompatible withvermicomposting. Within such an illustrative method, the drilling fluidis formulated to include linear paraffin having 11-18 carbon atoms, anon-oleaginous phase, and an emulsifying agent. In one illustrativeembodiment, the method includes mixing the drilling cuttings with acompostable waste material so as to provide a compostable balance ofnitrogen and carbon content. Within one such illustrative embodiment thenitrogen and carbon content have a ratio of about 2:1 to about 100:1 andmore preferably the nitrogen and carbon content has a ratio of about25:1. In one embodiment of the present invention, the vermicomposting iscarried out in a bioreactor and in such instances the vermiculturebioreactor is selected from a bin vermicomposter, a rotating drumvermicomposter, windrows and combinations of these. The drilling fluidutilized in the above noted illustrative embodiment should be formulatedsuch that it is useful in the drilling of subterranean wells. In onesuch instance the drilling fluid includes a weighting agent, a fluidloss control agent and/or similar such compounds typically utilized inthe formulation of drilling fluids. Of importance is that suchalternative components of the drilling fluid should not substantiallyharm the biocompatability of the drill cuttings with vermiculture.Likewise, the non-oleaginous fluid utilized in the above illustrativeembodiment should not substantially harm the biocompatability of thedrill cuttings with vermiculture. In one preferably illustrativeembodiment, the non-oleaginous fluid is selected from fresh water, seawater, a brine containing organic or inorganic dissolved salts, a liquidcontaining water-miscible organic compounds, combinations of these andsimilar compounds. As previously noted, the emulsifying agent utilizedin the formulation of the drilling fluids used in the above notedillustrative embodiments can be selected from a wide range of suitableemulsifying agents. However, such selection is made such that theemulsifying agent is does not substantially harm the biocompatability ofthe drill cuttings with verminculture. One such preferred emulsifyingagent is an eurisic diglyceride.

[0209] One of ordinary skill in the art should also appreciate andunderstand that the present invention also includes a vermiculture feedcomposition. One such illustrative vermiculture feed compositionincludes oil-contaminated solids, a bulking agent, and a compostablenitrogen source.

[0210] Within such an illustrative embodiment, the oil-contaminatedsolids are selected from drill cuttings, drilling mud, oil contaminatedsoil, combinations of these and similar compositions in which abiocompatible material is contaminated with oil. The illustrativevermiculture feed composition preferably includes a cellulose basedbulking agent such as sawdust, wood shavings, rice hulls, canola husks,shredded newsprint/paper; shredded coconut hulls, cotton seed hulls,mixtures of these and similar materials. Similarly, the illustrativevermiculture feed composition preferably includes a compostable nitrogensource preferably selected from yard or household wastes, foodpreparation or processing wastes, paunch or rumen material or similaranimal rendering wastes, sewage sludge from a water treatment facilityand mixtures of these and other similar materials. The illustrativevermiculture compositions preferably have a carbon to nitrogen ratio anda moisture content that is compatible with vermicomposting of thecompositions. More preferably the carbon to nitrogen ratio is about 25:1and the moisture content is about 75% by weight. In one illustrativeembodiment, the vermiculture composition also includes pretreated orpre-composted materials such as municipal waste or industrial wastematerials. Alternatively, the vermiculture composition is pre-treated orpre-composed prior to being used in vermiculture.

[0211] The present invention also includes the products of the processdisclosed herein. That is to say the present invention includes avermicast composition including: vermicast and biodegraded drillcuttings. Such composition is useful as organic material or compostmaterial for domestic gardening or commercial farming.

[0212] While the apparatus, compositions and methods of this inventionhave been described in terms of preferred or illustrative embodiments,it will be apparent to those of skill in the art that variations may beapplied to the process described herein without departing from theconcept and scope of the invention. All such similar substitutes andmodifications apparent to those skilled in the art are deemed to bewithin the scope and concept of the invention.

What is claimed is:
 1. A biodegradable wellbore fluid comprising: anoleaginous phase substantially composed of a linear paraffin having11-18 carbon atoms, a non-oleaginous phase containing a salt of abiodegradable anion, and an emulsifying agent in a concentration capableof forming an invert emulsion suitable for use as a drilling fluid. 2.The fluid of claim 1 wherein the oleaginous phase comprises from about30 to 99% by volume of the fluid and wherein the non-oleaginous phasecomprises from about 1% to about 70% by volume of the fluid.
 3. Thefluid of claim 2 wherein the non-oleaginous phase is substantially freeof halogen ions.
 4. The fluid of claim 2 wherein the non-oleaginousphase is selected from, fresh water, a brine containing organic orinorganic dissolved salts, a liquid containing water-miscible organiccompounds, and combinations thereof.
 5. The fluid of claim 1 wherein theemulsifying agent is eurisic diglyceride.
 6. The fluid of claim 1further comprising a weighting agent selected from the group consistingof calcium carbonate, hematite, ilmenite, barite, mullite, gallena,magnanese oxides, iron oxides and combinations thereof.
 7. The fluid ofclaim 1 further comprising a fluid-loss reducing agent.
 8. The fluid ofclaim 1 further comprising a viscosifying agent.
 9. The fluid of claim 8wherein the viscosifying agent is an organophilic clay.
 10. A method ofproducing a biodegradable wellbore fluid, the method comprising:blending an oleaginous phase substantially composed of a linear paraffinhaving 11-18 carbon atoms, a non-oleaginous phase containing a salt of abiodegradable anion and substantially free of halogen ions, and anemulsifying agent in a concentration capable of forming an invertemulsion suitable for use as a drilling fluid, in amounts sufficent soas to produce a biodegradable wellbore fluid.
 11. A method of drilling awellbore comprising, attaching a drilling bit to a length of drill pipe,rotating the drilling bit so as to form the wellbore, ciculating adrilling fluid through the drill pipe and the wellbore so as to removethe cuttings from around the drilling bit and out of the wellbore, andseparating the cuttings from the drilling fluid, wherein the drillingfluid is a biodegradable wellbore fluid including an oleaginous phasesubstantially composed of a linear paraffin having 11-18 carbon atoms, anon-oleaginous phase contains a salt of a biodegradable anion, and anemulsifying agent in a concentration capable of forming an invertemulsion suitable for use as a drilling fluid.
 12. The method of claim11, wherein the oleaginous phase is substantially free of halogen ion.13. The method of claim 11 further comprising bioremediating thecuttings after separating the cuttings from the drilling fluid.
 14. Themethod of claim 13 wherein the bioremediating of the cuttings is carriedout using a method selected from: landfarming, reacting in a bioreactor,conventional composting, vermiculture composting and combinationsthereof.
 15. A method of bioremediating wellbore cuttings comprising:drilling a subterranean well using a drilling fluid including anoleaginous phase substantially composed of a linear paraffin having11-18 carbon atoms, a non-oleaginous phase contains a salt of abiodegradable anion, and an emulsifying agent in a concentration capableof forming an invert emulsion suitable for use as a drilling fluid;removing the cuttings from the well; transporting the cuttings to aremediation site; blending the cuttings with nutrients to create atreatment feed, and bioremediating said treatment feed so as tosubtantially bioremediate the cutting.
 16. The method of claim 15,wherein the non-oleaginous phase is substantially free of halogen ions.17. The method of claim 15 wherein the treatment feed is formed into aslurry and the slurry is placed in a bioreactor and bacteria perform thebio-remediation.
 18. The method of claim 15 wherein the treatment feedis pretreated in a compost vessel prior to being formed into a slurry.19. A soil amendment comprising: drill cuttings from a wellbore, whereinsaid wellbore was drilled using a drilling fluid including an oleaginousphase substantially composed of a linear paraffin having 11-18 carbonatoms, a non-oleaginous phase containing the salt of a biodegradableanion, and an emulsifying agent in a concentration capable of forming aninvert emulsion suitable for use as a drilling fluid, and a bulkingagent.
 20. The soil amendment of claim 19, wherein the non-oleaginousphase is substantially free of halogen ion.
 21. The soil amendment ofclaim 20 wherein the drill cuttings are formed into a drill cuttingsslurry and the drill cuttings slurry is placed in a bioreactor andbacteria perform the bio-remediation.
 22. The method of claim 20 whereinthe non-oleaginous phase is substantially free of halide ions.
 23. Thesoil amendment of claim 20 wherein the bulking agent is selected fromsawdust, wood shavings, rice hulls, canola husks, shreddednewsprint/paper; shredded coconut hulls, cotton seed hulls, and mixturesof these
 24. The soil amendment of claim 20 wherein the emulsifyingagent is eurisic diglyceride.
 25. A method comprising biodegrading byvermicomposting drilling cuttings coated with a drilling fluid, whereinthe drilling fluid formulation includes a linear paraffin having 11-18carbon atoms, a non-oleaginous phase, and an emulsifying agent.
 26. Themethod of claim 25 further comprising mixing the drilling cuttings witha compostable waste material so as to provide a compostable balance ofnitrogen and carbon content.
 27. The method of claim 25 wherein thenitrogen and carbon content have a ratio of about 2:1 to about 100:1.28. The method of claim 25 wherein the nitrogen and carbon content havea ratio of about 25:1.
 29. The method of claim 25 wherein thevermicomposting is carried out in a bioreactor from a binvermicomposter, a rotating drum vermicomposter, windrows or combinationsof these.
 30. The method of claim 25 wherein the drilling fluid furtherincludes a weighting agent.
 31. The method of claim 25 wherein thenon-oleaginous fluid is selected from fresh water, sea water, a brinecontaining organic or inorganic dissolved salts, a liquid containingwater-miscible organic compounds, and combinations thereof.
 32. Themethod of claim 25 wherein the emulsifying agent is a eurisicdiglyceride.
 33. A method for biodegrading drilling cuttings coated witha drilling fluid, the method comprising: exposing the drilling cuttingsto a vermicomposting environment for a sufficient period of time topermit the worms to biodegrade the organic components of the drillingfluid.
 34. The method of claim 33 wherein the drilling fluid isformulated to include a linear paraffin having 11-18 carbon atoms, anon-oleaginous phase, and an emulsifying agent.
 35. The method of claim33 further comprising mixing the drilling cuttings with a compostablewaste material so as to provide a compostable balance of nitrogen andcarbon content.
 36. The method of claim 33 wherein the nitrogen andcarbon content have a ratio of about 2:1 to about 100:1.
 37. The methodof claim 33 wherein the nitrogen and carbon content have a ratio ofabout 25:1.
 38. The method of claim 33 wherein the vermicomposting iscarried out in a bioreactor selected from a bin vermicomposter, arotating drum vermicomposter, windrows and combinations of these. 39.The method of claim 33 wherein the drilling fluid further includes aweighting agent.
 40. The method of claim 33 wherein the non-oleaginousfluid is selected from fresh water sea water, a brine containing organicor inorganic dissolved salts, a liquid containing water-miscible organiccompounds, and combinations thereof.
 41. The method of claim 33 whereinthe emulsifying agent is a eurisic diglyceride.
 42. A method ofvermicular bio-remediation of oil contaminated solids, the methodcomprising providing the oil contaminated solids to a vermicularbioreactor, and allowing the worms within the vermicular bioreactor tobiodegrade the oil contaminated solids.
 43. The method of claim 42wherein the drilling fluid is formulated to include a linear paraffinhaving 11-18 carbon atoms, a non-oleaginous phase, and an emulsifyingagent.
 44. The method of claim 42 further comprising mixing the drillingcuttings with a compostable waste material so as to provide acompostable balance of nitrogen and carbon content.
 45. The method ofclaim 42 wherein the nitrogen and carbon content have a ratio of about2:1 to about 100:1.
 46. The method of claim 42 wherein the nitrogen andcarbon content have a ratio of about 25:1.
 47. The method of claim 42wherein the vermiculture bioreactor is selected from a binvermicomposter, a rotating drum vermicomposter, windrows andcombinations of these.
 48. The method of claim 42 wherein the drillingfluid further includes a weighting agent.
 49. The method of claim 42wherein the drilling fluid further includes a fluid loss control agent.50. The method of claim 42 wherein the non-oleaginous fluid is selectedfrom fresh water, sea water, a brine containing organic or inorganicdissolved salts, a liquid containing water-miscible organic compounds,and combinations thereof.
 51. The method of claim 42 wherein theemulsifying agent is a eurisic diglyceride.
 52. A vermiculture feedcomposition comprising: oil contaminated solids, a bulking agent, and acompostable nitrogen source.
 53. The vermiculture feed composition ofclaim 52 wherein the oil contaminated solids are selected from drillcuttings, drilling mud, oil contaminated soil, and combinations thereof.54. The vermiculture feed composition of claim 52 wherein the bulkingagent is selected from sawdust, wood shavings, rice hulls, canola husks,shredded newsprint/paper; shredded coconut hulls, cotton seed hulls, andmixtures of these.
 55. The vermiculture feed composition of claim 52wherein the compostable nitrogen source is selected from yard wastes,household wastes, farm wastes, food preparation wastes, food processingwastes, paunch material, rumen material, animal rendering wastes, sewagesludge, and mixtures of these.
 56. The vermiculture feed compositions ofclaim 52 wherein the compositions have a carbon to nitrogen ratio ofabout 25:1 and a moisture content of about 75% by weight.
 57. Thevermiculture feed compositions of claim 52 wherein the compositionfurther includes pretreated or pre-composted materials.
 58. Thevermiculture composition of claim 52 wherein the composition ispre-treated or pre-composed prior to being used in vermiculture.
 59. Avermicast composition comprising vermicast and biodegraded drillcuttings.